Effects of dissolved organic carbon and second substrates on the biodegradation of organic compounds at low concentrations

Abstract

Pseudomonas acidovorans and Pseudomonas sp. strain ANL but not Salmonella typhimurium grew in an inorganic salts solution. The growth of P. acidovorans in this solution was not enhanced by the addition of 2.0 jig of phenol per liter, but the phenol was mineralized. Mineralization of 2.0 jig of phenol per liter by P. acidovorans was delayed 16 h by 70 ,ug of acetate per liter, and the delay was lengthened by increasing acetate concentrations, whereas phenol and acetate were utilized simultaneously at concentrations of 2.0 and 13 jig/liter, respectively. Growth of Pseudomonas sp. in the inorganic salts solution was not affected by the addition of 3.0 jig each of glucose and aniline per liter, nor was mineralization of the two compounds detected during the initial period of growth. However, mineralization of both substrates by this organism occurred simultaneously during the latter phases of growth and after growth had ended at the expense of the uncharacterized dissolved organic compounds in the salts solution. In contrast, when Pseudomonas sp. was grown in the salts solution supplemented with 300 jig each of glucose and aniline, the sugar was mineralized first, and aniline was mineralized only after much of the glucose carbon was converted to CO2. S. typhimurium failed to multiply in the salts solution with 1.0 jig of glucose per liter. It grew slightly but mineralized little of the sugar at 5.0 jig/liter, but its population density rose at 10 jig of glucose per liter or higher. The hexose could be mineralized at 0.5 jig/liter, however, if the solution contained 5.0 mg of arabinose per liter. In solutions with this arabinose concentration and glucose levels too low to support growth, the percentage of glucose carbon incorporated into S. typhimurium cells was the same as when the bacterium was grown in solutions with high concentrations of glucose alone. When glucose was the only carbon source for S. typhimurium, the percentage of the glucose carbon assimilated and mineralized progressively declined as the sugar concentration was reduced to levels approaching the threshold for growth. These results indicate that second substrates and uncharacterized dissolved organic carbon may play an important role in controlling the rate and extent of biodegradation of organic compounds at low concentrations. Microorganisms can degrade a variety of synthetic organic compounds present in samples from natural environments at concentrations below 10 puglliter (1, 16). However, it is not certain whether microorganisms can grow at such low concentrations. It has been postulated that substrate uptake will just meet maintenance energy requirements and growth is not possible at sufficiently low substrate concentrations (12). * Corresponding author. to use the uncharacterized DOC were used. In addition, to understand the effect of DOC on the metabolism of synthetic organic substrates, studies were also conducted on the effects of second substrates on the biodegradation of low concentrations of organic compounds. MATERIALS AND METHODS Rad...

Kinetics of Growth and Aniline Degradation by Stenotrophomonas maltophilia

“…In several anilinedegrading microorganisms, aniline catabolism is repressed by the presence of other organic substrates (Aoki et aI., 1984;Helm and Reber] 979;Nakanishi et aI., 1991;and Zeyer et aI., 1985). Similar phenomena have been observed with other aromatic substrates (Heiman andCooper, 1987, andSchmidt andAlexander, 1985). However, there are some microorganisms that metabolize aniline in the presence of a high concentration of organic substrates (Aoki et aI., 1983, andKonopca et aI., 1989).…”

Epilithic metabolism of dissolved organic carbon in boreal forest rivers

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Inhibitory effects of high molecular weight dissolved organic matter upon metabolic processes in biofilms from contrasting rivers and streams

“…Thus the remuval of these substances apparently permits a greater level of metabolic heat output than would otherwise oecur. General evidence for inhibitory substances has come from the work of Schmidt & Alexander (1985) working on axenie cultures, Chudoba (1985) working on activated sludge and Klein & Alexander (1986) working in freshwater. Most recently Marxsen (1987 and unpublished) has postulated the existence of sueh substances to account for deviation from saturation of ' ""C glucose uptake kinetics by microorganisms in acidic streams.…”